For most of us, it’s hard to get the requisite 7–9 hours of sleep a night. But before you think getting nine or more hours of sleep is like extra credit, think again. The next time you’re tempted to sleep in, consider how big an impact extra sleep can have on your health (and not necessarily in a good way).
Sleeping just one hour extra on weekends was linked to impaired insulin sensitivity, increased calorie consumption and weight gain, according to new research published in the journal Current Biology. The research also showed getting “recovery sleep” on weekends distorted circadian rhythms and led to more late-night snacking.
Here are four more health-related reasons to resist the urge to sleep in:
Getting as little as two additional hours of sleep was associated with an increased risk of stroke, heart disease and death, according to 2018 research published in the European Heart Journal. In some cases, napping also increased the risks — with one notable exception: Those who slept less than six hours per night and took afternoon naps to compensate for the lack of sleep helped reduce their risk of major cardiovascular events.
In a statement, co-author Salim Yusuf, professor of medicine at McMaster University, said, “The general public should ensure that they get about 6–8 hours of sleep a day. On the other hand, if you sleep too much regularly, say more than nine hours a day, then you may want to visit a doctor to check your overall health.”
If you want to reduce your risk of developing Type 2 diabetes, eat nutritious foods, exercise, watch your weight and set the alarm clock. Several studies have found links between oversleeping and Type 2 diabetes, including research published in Diabetes Care, which found each additional hour of sleep over eight hours per night was associated with an increased risk of developing the disease.
It’s unclear how sleeping late increases the risk of Type 2 diabetes, but researchers suspect oversleeping could be related to other health issues such as sedentary lifestyle and low socioeconomic status, which are both risk factors for Type 2 diabetes.
The more you sleep, the more you’ll weigh, according to one 2019 study. Researchers found adults who slept more than nine hours per night had a higher body mass index than those who logged between 5–8 hours under the covers. Additional research showed long sleep duration was a risk factor for obesity. Co-author Justin B. Moore, PhD, associate professor at Wake Forest School of Medicine, suspects more time in bed means less time for physical activities.
“If I were going to make an educated guess, I’d say it’s a combination of depression and poor sleep quality causing obesity rather than the time spent asleep,” he says.
A review of 65 studies, which included more than 1.5 million participants, found long sleep duration was associated with increased colorectal cancer risk; a separate study found sleeping for more than eight hours per night was linked to a higher risk of cancers related to estrogen, including breast and ovarian cancers.